Particle production from DM annihilation/decay processes is dominated by QCD jet fragmentation.This is true for DM masses above a few GeV producing hadronic final states either directly through e.g. \(\chi \chi \rightarrow q\bar{q}\)  or indirectly via the decays of the intermediate heavy resonances such as the \(W/Z/H\)  bosons or the top quark. Final state stable particles such as photons or positrons are then produced as a result of a complicated set of processes which includes QED and QCD radiations, hadronisation, and hadron decays. Unlike parton-level scattering amplitudes at e.g. the lowest order of perturbation theory, the problem of hadronisation cannot be solved from first-principles. Jet universality tells us that hadronisation is a universal process that can be factorised off the short-distance processes e.g. DM annihilation. Phenomenological models such that Fragmentation Functions [1]} or explicit dynamical models such as the string [2]}, [3]} or cluster [4]}, [5]} models which are embedded in Monte Carlo (MC) event generators [6]} are the up-to-date solutions to the hadronisation problem. The essential point is that the fragmentation models' parameters are to a very good approximation independent of the short-distance processes; therefore, they can be determined from fits to existing data such as \(e^+ e^- \rightarrow \mathrm {hadrons}\)  and used to make predictions for e.g. DM annihilation.
